Highly upregulated in liver cancer (HULC): An update on its role in carcinogenesis

Highly upregulated in liver cancer (HULC) was initially recognized during the screening of a hepatocellular carcinoma (HCC)-specific gene library. Further studies demonstrated its aberrant upregulation in several other tumor types. The oncogenic roles of this long noncoding RNA (lncRNA) have been verified through expression studies as well as functional studies. Moreover, the results of knockdown experiments have indicated diminished carcinogenic effects of cancer cell line in nude mice following HULC silencing. More recent studies have shown that expression levels of this lncRNA might be used as diagnostic biomarkers in cancer patients. Moreover, mechanistical studies have revealed associations between HULC and two HCC-related viruses namely hepatitis B and C viruses. Taken together, HULC can be regarded as a therapeutic target not only for HCC but also for a variety of human malignancies. In the current review, we summarized the recent literature about the role of HULC in the carcinogenesis and its potential application in cancer diagnosis and prognosis.     

LncRNAs as potential diagnostic and prognostic biomarkers in gastric cancer: A novel approach to personalized medicine

Gastric cancer is the third leading cause of cancer death with 5-year survival rate of about 30–35%. Since early detection is associated with decreased mortality, identification of novel biomarkers for early diagnosis and proper management of patients with the best response to therapy is urgently needed. Long noncoding RNAs (lncRNAs) due to their high specificity, easy accessibility in a noninvasive manner, as well as their aberrant expression under different pathological and physiological conditions, have received a great attention as potential diagnostic, prognostic, or predictive biomarkers. They may also serve as targets for treating gastric cancer. In this review, we highlighted the role of lncRNAs as tumor suppressors or oncogenes that make them potential biomarkers for the diagnosis and prognosis of gastric cancer. Relatively, lncRNAs such as H19, HOTAIR, UCA1, PVT1, tissue differentiation-inducing nonprotein coding, and LINC00152 could be potential diagnostic and prognostic markers in patients with gastric cancer. Also, the impact of lncRNAs such as ecCEBPA, MLK7-AS1, TUG1, HOXA11-AS, GAPLINC, LEIGC, multidrug resistance-related and upregulated lncRNA, PVT1 on gastric cancer epigenetic and drug resistance as well as their potential as therapeutic targets for personalized medicine was discussed.     

Taurine-upregulated gene 1: A functional long noncoding RNA in tumorigenesis

Taurine-upregulated gene 1 (TUG1) is a 7.1 kb long noncoding RNA (lncRNA) first recognized in 2005 as an important element for retinal development in rodents. Subsequently, this lncRNA has been shown to participate in oncogenic processes through alteration in chromatin structure, sponging microRNAs, and affecting the expression of some cancer-related pathways. While most of the studies have revealed an oncogenic role for this lncRNA, some reports have shown downregulation of TUG1 in lung cancer samples compared with noncancerous samples. In triple negative breast cancer samples, the expression of this lncRNA has been decreased. Besides, its expression has been higher in HER2-enriched and basal-like subtypes compared with luminal A. In the current review, we discuss the latest literature about the expression pattern and functional roles of TUG1 in diverse cancer types. In addition, its role in epithelial−mesenchymal transition and activation of Wnt/β-catenin pathway in human malignancies will be explored.     

LncRNA PVT1 predicts prognosis and regulates tumor growth in prostate cancer

Long non-coding RNA (lncRNA) plasmacytoma variant translocation 1(PVT1) was aberrantly expressed in various cancers and is associated with tumor prognosis. Here, we aim to investigate its function in prostate cancer. Small interfering RNA against PVT1 was transfected into prostate cancer cell lines and cell growth and apoptosis were analyzed. Our results showed that PVT1 was overexpressed in prostate cancer tissues and cells. Higher levels of PVT1 indicated poorer overall survival and disease-free survival. A significant association was found between PVT1 expression and tumor stage. Besides, PVT1 knockdown significantly inhibited prostate cancer growth in vivo and in vitro and promoted cell apoptosis. PVT1 knockdown also significantly upregulated the expression of cleaved caspase-3 and cleaved caspase-9, but downregulated the expression of c-Myc in prostate cancer cell lines. Our results suggest that PVT1 played an oncogenic role in prostate cancer and could be used as a potential biomarker for diagnosis of prostate cancer.     

Long non-coding RNA Linc00152 is involved in cell cycle arrest,apoptosis, epithelial to mesenchymal transition,cell migration and invasion in gastric cancer

Gastric cancer remains a serious threat to public health with high incidence and mortality worldwide. Accumulating evidence demonstrates that long non-coding RNAs (lncRNAs) play important roles in regulating gene expression and are involved in various pathological processes, including gastric cancer. To investigate the possible role of dysregulated lncRNAs in gastric cancer development, we performed lncRNA microarray and identified 3141 significantly differentially expressed lncRNAs in gastric cancer tissues. Next, some of deregulated lncRNAs were validated among about 60 paired gastric cancer specimens such as Linc00261, DKFZP434K028, RPL34-AS1, H19, HOTAIR and Linc00152. Our results found that the decline of DKFZP434K028 and RPL34-AS1, and the increased expression of Linc00152 positively correlated with larger tumor size. The high expression levels of HOTAIR were associated with lymphatic metastasis and poor differentiation. Since the biological roles of Linc00152 are largely unknown in gastric cancer pathogenesis, we assessed its functions by silencing its up-regulation in gastric cancer cells. We found that Linc00152 knockdown could inhibit cell proliferation and colony formation, promote cell cycle arrest at G1 phase, trigger late apoptosis, reduce the epithelial to mesenchymal transition (EMT) program, and suppress cell migration and invasion. Taken together, we delineate the gastric cancer lncRNA signature and demonstrate the oncogenic functions of Linc00152. These findings may have implications for developing lncRNA-based biomarkers for diagnosis and therapeutics for gastric cancer.     

Long non‐coding PANDAR as a novel biomarker in human cancer: A systematic review

Objectives

Long non‐coding RNAs (lncRNAs) are characterized as a group of RNAs that more than 200 nucleotides in length and have no protein‐coding function. More and more evidences provided that lncRNAs serve as key molecules in the development of cancer. Deregulation of lncRNAs functions as either oncogenes or tumour suppressor genes in various diseases. Recently, increasing studies about PANDAR in cancer progression were reported. In our review, we will focus on the current research on the character of PANDAR include the clinical management, tumour progression and molecular mechanisms in human cancers.

Materials and methods

We summarize and analyze current studies concerning the biological functions and mechanisms of lncRNA PANDA in tumour development. The related studies were obtained through a systematic search of Pubmed.

Results

PANDAR was a well‐characterized oncogenic lncRNA and widely overexpressed in many tumours. PANDAR is upregulated in many types of cancer, including colorectal cancer, lung cancer, renal cell carcinoma, cholangiocarcinoma, osteosarcoma, thyroid cancer and other cancers. Upregulation of PANDAR was significantly associated with advanced tumour weights, TNM stage and overall survival. Furthermore, repressed of PANDAR would restrain proliferation, migration and invasion.

Conclusion

PANDAR may act as a powerful tumour biomarker for cancer diagnosis and treatment.     

A prognostic 11 long noncoding RNA expression signature for breast invasive carcinoma

Breast cancer, the most common cancer in women worldwide, is associated with high mortality. The long non-coding RNAs (lncRNAs) with a little capacity of coding proteins is playing an increasingly important role in the cancer paradigm. Accumulating evidences demonstrate that lncRNAs have crucial connections with breast cancer prognosis while the studies of lncRNAs in breast cancer are still in its primary stage. In this study, we collected 1052 clinical patient samples, a comparatively large sample size, including 13 159 lncRNA expression profiles of breast invasive carcinoma (BRCA) from The Cancer Genome Atlas database to identify prognosis-related lncRNAs. We randomly separated all of these clinical patient samples into training and testing sets. In the training set, we performed univariable Cox regression analysis for primary screening and played the model for Robust likelihood-based survival for 1000 times. Then 11 lncRNAs with a frequency more than 600 were selected for prediction of the prognosis of BRCA. Using the analysis of multivariate Cox regression, we established a signature risk-score formula for 11 lncRNA to identify the relationship between lncRNA signatures and overall survival. The 11 lncRNA signature was validated both in the testing and the complete set and could effectively classify the high-/low-risk group with different OS. We also verified our results in different stages. Moreover, we analyzed the connection between the 11 lncRNAs and the genes of ESR1, PGR, and Her2, of which protein products (ESR, PGR, and HER2) were used to classify the breast cancer subtypes widely. The results indicated correlations between 11 lncRNAs and the gene of PGR and ESR1. Thus, a prognostic model for 11 lncRNA expression was developed to classify the BRAC clinical patient samples, providing new avenues in understanding the potential therapeutic methods of breast cancer.     

The long non‐coding RNA PVT1 represses ANGPTL4 transcription through binding with EZH2 in trophoblast cell

Despite progress in diagnostics and treatment for preeclampsia, it remains the foremost cause of maternal and foetal perinatal morbidity and mortality worldwide. Over recent years, various lines of evidence have emphasized long non‐coding RNAs (lncRNAs) which function as an innovative regulator of biological behaviour, as exemplified by proliferation, apoptosis and metastasis. However, the role of lncRNAs has not been well described in preeclampsia. Here, we identified a lncRNA, PVT1, whose expression was down‐regulated in qRT‐PCR analyses in severe preeclampsia. The effects of PVT1 on development were studied after suppression and overexpression of PVT1 in HTR‐8/SVneo and JEG3 cells. PVT1 knockdown notably inhibited cell proliferation and stimulated cell cycle accumulation and apoptosis. Exogenous PVT1 significantly increased cell proliferation. Based on analysis of RNAseq data, we found that PVT1 could affect the expression of numerous genes, and then investigated the function and regulatory mechanism of PVT1 in trophoblast cells. Further mechanistic analyses implied that the action of PVT1 is moderately attributable to its repression of ANGPTL4 via association with the epigenetic repressor Ezh2. Altogether, our study suggests that PVT1 could play an essential role in preeclampsia progression and probably acts as a latent therapeutic marker; thus, it might be a useful prognostic marker when evaluating new therapies for patients with preeclampsia.     

Long non‐coding RNA NNT‐AS1 sponges miR‐424/E2F1 to promote the tumorigenesis and cell cycle progression of gastric cancer

Long non‐coding RNAs (lncRNAs) have been illustrated to function as important regulators in carcinogenesis and cancer progression. However, the roles of lncRNA NNT‐AS1 in gastric cancer remain unclear. In the present study, we investigate the biological role of NNT‐AS1 in gastric cancer tumorigenesis. Results revealed that NNT‐AS1 expression level was significantly up‐regulated in GC tissue and cell lines compared with adjacent normal tissue and normal cell lines. The ectopic overexpression of NNT‐AS1 indicated the poor prognosis of GC patients. In vitro experiments validated that NNT‐AS1 knockdown suppressed the proliferation and invasion ability and induced the GC cell cycle progression arrest at G0/G1 phase. In vivo xenograft assay, NNT‐AS1 silencing decreased the tumour growth of GC cells. Bioinformatics online program predicted that miR‐424 targeted the 3′‐UTR of NNT‐AS1. Luciferase reporter assay, RNA‐immunoprecipitation (RIP) and RNA pull‐down assay validated the molecular binding within NNT‐AS1 and miR‐424, therefore jointly forming the RNA‐induced silencing complex (RISC). Moreover, E2F1 was verified to act as the target gene of NNT‐AS1/miR‐424, indicating the NNT‐AS1/miR‐424/E2F1 axis. In conclusion, our study indicates that NNT‐AS1 sponges miR‐424/E2F1 to facilitate GC tumorigenesis and cycle progress, revealing the oncogenic role of NNT‐AS1 for GC.     

Identification of key lncRNAs in the carcinogenesis and progression of colon adenocarcinoma by co-expression network analysis

Colon adenocarcinoma (COAD) is one of the most common cancers, and its carcinogenesis and progression is influenced by multiple long non-coding RNAs (lncRNA), especially through the miRNA sponge effect. In this study, more than 4000 lncRNAs were re-annotated from the microarray datasets through probe sequence mapping to obtain reliable lncRNA expression profiles. As a systems biology method for describing the correlation patterns among genes across microarray samples, weighted gene co-expression network analysis was conducted to identify lncRNA modules associated with the five stepwise stages from normal colonic samples to COAD (n = 94). In the most relevant module (R² = −0.78, P = 4E-20), four hub lncRNAs were identified (CTD-2396E7.11, PCGF5, RP11-33O4.1, and RP11-164P12.5). Then, these four hub lncRNAs were validated using two other independent datasets including GSE20916 (n = 145) and GSE39582 (n = 552). The results indicated that all hub lncRNAs were significantly negatively correlated with the three-stage colonic carcinogenesis, as well as TNM stages in COAD (one-way analysis of variance P < 0.05). Kaplan-Meier survival curve showed that patients with higher expression of each hub lncRNA had a significantly higher overall survival rate and lower relapse risk (log-rank P < 0.05). In conclusion, through co-expression analysis, we identified and validated four key lncRNAs in association with the carcinogenesis and progression of COAD, and these lncRNAs might have important clinical implications for improving the risk stratification, therapeutic decision and prognosis prediction in COAD patients.     

DNA methylation and gene expression profiles characterize epigenetic regulation of lncRNAs in colon adenocarcinoma

The long noncoding RNAs (lncRNAs) are associated with tumorigenesis and progression of cancer. While DNA methylation is a common epigenetic regulator of gene expression, the methylation of lncRNAs was rarely studied. To address this gap, we integrated DNA methylation and RNA-seq data to characterize the landscape of lncRNA methylation in colon adenocarcinoma (COAD). We collected and analyzed the lncRNA expression and methylation data from The Cancer Genome Atlas and Cancer Cell Line Encyclopedia to identify the epigenetically regulated lncRNAs. We further investigated the biological and clinical relevance of the identified lncRNAs via bioinformatics analysis. We identified 20 epigenetically upregulated lncRNAs in COAD, including several well-studied lncRNAs whose methylation regulation were poorly investigated, such as PVT1 and UCA1. We also revealed several novel tumor-associated lncRNAs in COAD, including GATA2-As1 and CYTOR. Next, we explored their biology function using gene set enrichment analysis and competitive endogenous RNA analysis. We characterized the methylation landscape of lncRNA in COAD and identified 20 epigenetically upregulated lncRNAs. Our findings will shed new light on the epigenetic regulation of lncRNA expression by DNA methylation.     

Long non‐coding RNA SNHG14 induces trastuzumab resistance of breast cancer via regulating PABPC1 expression through H3K27 acetylation

Currently, resistance to trastuzumab, a human epidermal growth factor receptor 2 (HER2) inhibitor, has become one major obstacle for improving the clinical outcome of patients with advanced HER2⁺ breast cancer. While cell behaviour can be modulated by long non‐coding RNAs (lncRNAs), the contributions of lncRNAs in progression and trastuzumab resistance of breast cancer are largely unknown. To this end, the involvement and regulatory functions of lncRNA SNHG14 in human breast cancer were investigated. RT‐qPCR assay showed that SNHG14 was up‐regulated in breast cancer tissues and associated with trastuzumab response. Gain‐ and loss‐of‐function experiments revealed that overexpression of SNHG14 promotes cell proliferation, invasion and trastuzumab resistance, whereas knockdown of SNHG14 showed an opposite effect. PABPC1 gene was identified as a downstream target of SNHG14, and PABPC1 mediates the SNHG14‐induced oncogenic effects. More importantly, ChIP assays demonstrated that lncRNA SNHG14 may induce PABPC1 expression through modulating H3K27 acetylation in the promoter of PABPC1 gene, thus resulting in the activation of Nrf2 signalling pathway. These data suggest that lncRNA SNHG14 promotes breast cancer tumorigenesis and trastuzumab resistance through regulating PABPC1 expression through H3K27 acetylation. Therefore, SNHG14 may serve as a novel diagnostic and therapeutic target for breast cancer patients.     

Long non-coding RNA DANCR promotes colorectal tumor growth by binding to lysine acetyltransferase 6A

Recent studies have demonstrated that long non-coding RNAs (lncRNAs) play critical roles in cancer development and progression. However, the mechanism by which lncRNAs contribute to colorectal cancer remains unclear. In this study, we identified the lncRNA, DANCR, which was upregulated in colorectal cancer. The upregulation of DANCR expression was associated with shorter patient survival time. DANCR depletion decreased cell proliferation, cell cycle progression, and tumorigenesis in a subcutaneous mouse xenograft model system. We further demonstrated that DANCR bound with lysine acetyltransferase 6A. This binding was essential for KAT6A acetyltransferase activity and thus, it influenced the expression of KAT6A target genes. Our data indicated that DANCR functions as an oncogenic lncRNA that promotes tumor development and progression. Therefore, DANCR may be a target molecule for colorectal cancer treatment.